A water and sewage treatment system using a rectangular clarifier is described in a co-pending application Ser. No. 722,047 filed Apr. 11, 1985 entitled "Water Treatment Plastics Products For Rectangular Clarifiers" of Hannum, now U.S. Pat. No. 4,645,598, issued Feb. 24, 1987.
Generally when process water is introduced to a sewage or water treatment plant for treatment solids, both inorganic and organic, are removed from the process water by means of clarification or settling in rectangular clarifiers. These clarifiers are known as primary and secondary clarifiers.
Prior to being introduced into the primary clarifiers, the pocess water receives preliminary treatment to remove large foreign particles or tramp debris; such as stones, wood, rock, glass, etc. The process water then is clarified in the primary clarifiers which allows the remaining solids, both, organic and inorganic, to either settle to the bottom of the tank or rise to the surface of the water for removal by the sludge/scum collector.
The removal of the sludge and scum is accomplished by the travel of a chain and flight collector which moves the sludge settled to the bottom of the clarifier to one end of the tank for eventual removal by a down stream process. The floating scum on the surface of the water is moved to the opposite end of the tank for removal by scum removal equipment. This removal of sludge and scum is generally accomplished in the primary clarifiers. Secondary clarifiers generally remove sludge only.
In recent years, in order to improve the level of treatment in wastewater treatment plants, oxygen has been introduced into the process water. Due to the presence of high levels of oxygen, components, traditionally manufactured of steel have corroded and required frequent replacement. In recent years, the steel components have been replaced by plastic flight members, shoes, stub shafts and the like.
Many clarifier tanks in Europe and the United States are often very wide, in the order of 100 feet. In the United States, when a clarifier is 100 feet wide, it is generally divided into individual bays having widths of 25 feet or less. These individual bays are normally divided by intermediate walls constructed of cast-in-place concrete or cast concrete. With the presence of these intermediate walls the attachment of the chain and flight collector system in each individual bay is accomplished by anchors placed in the intermediate concrete wall. In tanks which do not have intermediate tank walls or in tanks in Europe, and other places which are not subdivided into two bays, collection of the sludge is accomplished by a single steel boom supported by massive above-water framework which requires heavy maintenance and high operating costs.
The installation of chain and flight rectangular sludge removal equipment in tanks that do not have intermediate walls requires a manufacturer to install massive concrete structures.
This invention involves generally dividing a relatively large tank into individual bays without the use or expense of massive concrete structures and to provide the necessary support for return rails on which flight members are disposed to ride.
Plastic elements are preferably used in the rail or wear members in water treatment systems because they are not adversely affected by water or chemicals in the water. At certain times, the tank may be empty and not in use. At such times the rail elements may be exposed to high temperatures from the sun, for example, and tend to expand. It is desirable in these cases to permit the rail elements to expand or contract in accordance with temperature conditions.